This invention relates to a new oil adsorbent capable of effectively eliminating oils floating on the surface of water or existing as droplets in water through adsorption.
Petroleum refining plants and petrochemical plants discharge industrial effluents containing a variety of waste oils. When such industrial effluents are thrown away into river and sea, a problem of environmental pollution is caused by waste oils. Accordingly, perfect elimination of oils is required for discharge of such industrial effluents from the plants in the field of petroleum industry.
In some cases, heavy oil is inadvertently discharged or leaked by mismanagement from tankers anchored in harbors. Such heavy oil has also to be eliminated as it damages seriously the harbor environment.
As the means for removing oils from water contaminated with the oils, there have been known, for example, a method using an oil separator to separate the contaminated water into an oily phase and an aqueous phase, a method for biologically decomposing oils with an active sludge, etc. As one of these known method, there is a method wherein an oil-absorbing substance as oil adsorbent is brought into contact with oil-contaminated water and then the oil adsorbent in which oils have been absorbed is separated from water. The method using an oil-absorbing substance as oil adsorbent has such a merit that it can remove not only oils floating on the surface of water but also oils present in water as droplets.
In this method, however, it is important what is utilizable as oil adsorbent. The oil adsorbent has to possess excellently high oil absorbability with a negligible water absorbability to adsorb oils effectively from water. As this material is used in a large amount, it also has to be less expensive and easily disposable, for example, by incineration treatment after the use for oil-adsorbing treatment. Heretofore used as such oil adsorbent are sawdust, straw-mat, unwoven cloth, polyurethane foam and other porous inorganic substances. However, all of these substances have low efficiency in catching oils from water and so are not satisfactory for practical use.